THERMODYNAMIC PACKER Filed Nov. 23, 1959 3 Sheets-Sheet 3 John E. Ortloff Inventor By W 8. Qu-L Attorney 3,653,321 Patented Sept. 11, 1962 3,053,321 THERMGDYNAMEC PACKER John E. Ortloif, Tulsa, Ulda, assignor to Jersey Production Research Company, a corporation of Delaware Filed Nov. 23, 1959, Ser. No. 854,654 6 Claims. (Cl. 1o6--l79) The present invention relates to apparatus for controlling the flow of fluids in boreholes and more particularly relates to an improved packer assembly which can be readily set in place in a borehole or wellbore without resort to the hydraulic or mechanical apparatus required to actuate packers of conventional design. In still greater particularity, the invention relates to a thermodynamic packer which is actuated in a borehole or wellbore by movement of a bimetallic element responsive to changes in temperature.

Packers of various types are used in a wide variety of oil field operations. In conjunction with air drilling, for example, they are frequently set into place on either side of an aquifer in order to permit the application of a sealing agent to the formation. In drill stem testing, they serve to isolate the strata to be tested so that an uncontaminated sample of the fluids contained therein can be recovered. In well completion operations, they are often used to direct the producing fluids into an inner string of tubing in the wellbore. In well stimulation processes, they are utilized to confine the stimulation fluid to the oil-bearing strata. In secondary recovery operations, they may be employed to direct displacing agents or hot gases into the proper strata in a reservoir. Many other applications might be cited.

The packer assemblies utilized heretofore generally fall into two classes, inflatable packers and mechanicallyactuated packers. The infllatable devices are those which are set into place Within the borehole or wellbore by filling them with fluid through an orifice in the drill string or tubing upon which the packer assembly is mounted. Devices of this type necessitate the use of the drill pipe or tubing to convey the fluid to the packer and require that a valve and mechanism for operating it be provided to open and close the orifice at the proper time. The mechanically-actuated packer assemblies generally depend upon the placement of slips and rotation of the drill string or tubing, the downward movement of the string or tubing against a member bearing on the bottom of the borehole or wellbore, or upon similar movement controlled from the surface. The apparatus required to set such packers is often complex and may occupy considerable space in the wellbore or borehole. In some cases, release of the packers after they have been set presents problems. Certain types cannot be released from the surface and must be drilled out, making their use expensive if they are not to be installed permanently. For these reasons, neither type of conventional packer has proved wholly satisfactory in all applications.

The present invention provides an improved type of packer for use in certain oil field operations which is free of many of the disadvantages associated with inflatable and mechanically actuated packers employed in the past. In accordance with the invention, it has now been found that movement of a bimetallic element in response to a change in the temperature within a borehole or wellbore can readily be utilized to set and later release a packer without the necessity for hydraulic or mechanical control from the surface. This permits the use of packers which are considerably simpler in construction and operation than those utilized heretofore and facilitates the carrying out of many operations requiring the use of a packer.

The improved thermodynamic packer assembly provided by the invention includes a supporting structure capable of being mounted upon a drill collar, tubing section, wellbore heater or similar device positioned in a borehole or wellbore, a bimetallic element which will move with respect to the supporting structure under the influence of a change in temperature, and a sealing element for closing off the annular space in the borehole or wellbore around the supporting structure in response to movement of the bimetallic element. The supporting structure utilized will depend largely upon the character of the device upon which it is to be mounted and may be varied considerably. A variety of bimetallic elements may be used. Obviously, the temperature conditions under which the packer assembly is to be set in the borehole or wellbore will be important in determining the bimetallic element to be employed. The sealing element will preferably be a flexible member of rubber, plastic or asbestos but the material utilized, as well as its arrangement on the supporting structure, will be governed to a large extent by the conditions in the wellbore or borehole and by the bimetallic element used.

The exact nature of the invention and its objects can be best understood by referring to the following detailed description of a number of apparatus embodiments and to the accompanying drawings, in which:

FIG. 1 is a vertical section through a thermodynamic packer assembly including bimetallic expansive elements positioned in a wellbore for use in conjunction with an in situ combustion operation;

FIG. 2 depicts the apparatus of FIG. 1 with the packer assembly set in the wellbore;

FIG. 3 is a cross section through the apparatus of FIG. 2 taken along the line 3-3;

FIG. 4 is a vertical view, partially in section, showing a wellbore heater provided with a packer actuated by bimetallic elements in accordance with the invention;

FIG. 5 is a vertical section through a thermodynamic packer employing a different type of bimetallic expansive elements; and

FIG. 6 is a cross section through the packer of FIG. 5 taken along the line 6-6.

Referring now to FIG. 1, reference numeral 11 designates casing positioned in a wellbore drilled into a multizone oil reservoir, the lower zone of which has been partially depleted by primary production techniques and is to be subjected to an in situ combustion secondary recovery process independently of the upper producing zone. The casing has been perforated opposite the lower producing zone of the reservoir, the perforations being indicated by reference numeral '12. The upper producing zone and the corresponding perforations in the casing opposite it are not shown in the drawing. The gases injected into the lower zone to initiate and support the combustion process are tranmitted through tubing 13 suspended within casing 11.

Packer support .14 is mounted at the lower end of tubing 13 just above the producing zone into which the hot gases required to initiate in situ combustion are to be injected. The supporting member is attached to the tubing by threads 15 or other suitable connecting means. The bore 16 of the supporting member forms an extension of the conduit in tubing 13 and hence fluids transmitted downwardly through the tubing emerge beneath the assembly adjacent the perforations 12 in casing 11. The outer surface of member 14 contains an annular groove 17 in which the expansive element 18 and the sealing member 19 employed in this embodiment of the invention are carried.

Expansive element 18 consists of a plurality of bimetallic strips atfixed at one end to supporting member 14 and extending radially therefrom at a downward angle in cantilever fashion. Each strip consists of two metals having different coefficients of thermal expansion. The metals making up the strips are bonded together and, as arranged in the apparatus of FIG. 1, the metal having the higher coefficient of expansion is placed on the lower side of each strip. The strips are preferably, trapezoidal in shape and fit closely together when in the unexpanded position shown in FIG. 1. The arrangement of the strips on supporting member 14 can be seen more clearly in FIG. 3 of the drawing.

Bimetallic strips 18 may be prepared from a variety of different metals, so long as the particular metals used have different coefiicients of thermal expansion. By properly selecting the metals and by controlling the dimensions of the strips, the expansion which occurs for a given change in temperature can be regulated. The metals employed should, of course, have melting points well above the temperatures at which the packer assembly is to be utilized. Metals which may be employed in various combinations include iron, nickel, copper, aluminum, zinc, manganese, tin, lead, tungsten, chromium and the like. Alloys may also be employed. Two alloys particularly suitable for use as the high and low expansive sides of a bimetallic element intended for use under high temperature conditions are as follows:

Low-Expansive Side Studies have shown that a cantilever strip made up of the two alloys described above measuring three inches long and one-sixteenth inch thick will deflect about onehalf inch as its temperature is increased from 200 F. to 600 F. Under the same conditions, a strip three inches long and one-eighth inch thick will deflect about one-fourth of an inch. This provides adequate movement for the setting of the packer under high temperature conditions such as those encountered in in situ combustion and similar operations. Other bimetallic elements made up of different metals will move greater or lesser distances under different temperature conditions and hence the temperature range over which the packer will set in place over a borehole or wellbore, as well as the degree of expansion which occurs with a given increase in temperature, can readily be controlled by utilizing the proper combination of metals.

Sealing member 19 is a flexible ring retained in notch 17 above expansive element 18. It is preferred that the sealing element be made of asbestos or similar heatresistant material in the case of packer assemblies intended for use at high temperatures such as those encountered in in situ combustion operations. Rubber or plastic sealing elements will generally be suitable for use in packers intended for low temperature operations. The outside diameter of sealing member 19 should be such that expansion of bimetallic strips 18 will force it against the casing or wall of the borehole in which the assembly is to be used. It is preferred that the sealing member be sufiiciently thick that it will be forced against the casing or borehole wall over a relatively large area, thus assuring a good, fluid-tight seal. The material from which the sealing member or packer is made must be flexible enough that it can conform to irregularities in the casing or borehole wall. This is particularly important in the case of packer assemblies intended for use in uncased wells.

In utilizing the apparatus shoWn in FIG. 1 of the drawing in an in situ combustion process of the type referred to heretofore, tubing 13 carrying the packer assembly at its lower end is first lowered into the wellbore until the assembly is located just above the perforations communicating with the formation in which the in situ combustion operation is to be carried out. Hot gases for initiating the combustion process, flue gases produced by burning a suitable fuel on the surface for example, are then passed downwardly through the tubing and assembly into the wellbore opposite the zone in which the combustion front is to be established. Since these gases will normally be several hundred degrees Fahrenheit above the ambient temperature in the wellbore, the temperature of the bimetallic strips will rapidly increase. As the strips expand due to this increase in temperature, they will force sealing member 19 outwardly until a tight seal in the annular space between casing 11 and supporting member 14- has been established. The packer is now set in place, as shown in FIG. 2 of the drawing. The pressure built up as gas is injected into the space beneath the packer is exerted against the under side of scaling member and helps maintain the seal. The injected gases flow into the formation through perforations 12 and hence the heat necessary to initiate the combustion process is transferred to the formation.

Hot gases are normally injected into the formation during an in situ combustion process until the formation has been heated to a temperature above the ignition temperature of the oil present in the reservoir. When this temperature is reached, the injection of hot gases is ordinarily halted and air, with or without inert gases, is supplied to the formation to support combustion and advance the combustion front. At this point, the bimetallic strips 18 on the packer assembly may begin to cool down and contract. Because of the high pressures utilized in such combustion processes, however, the pressure on the underside of sealing element 19, not aflixed to bimetallic strips 18, will normally be suflicient to maintain the element in a distended position against casing 11. This pressure may range up to about 1500 pounds per square inch or higher and hence it is preferred that the portion of supporting member 14 above sealing element 19 be designed so that it will support the distended sealing member as shown in FIG. 2. Release of the pressure after the bimetallic strips have returned to their unexpanded position will permit withdrawal of the apparatus from the borehole or wellbore.

It will be seen from the foregoing that the thermodynamic packer of the invention provides a useful tool for controlling fluid circulation in a borehole or wellbore during a secondary recovery process utilizing in situ combustion. The packer assembly described in conjunction with FIGURES 1 through 3 of the drawing is not limited to the specific process described above, however, and will find application in a number of other operations wherein changes in the wellbore temperature occur. It may be used equally well in conjunction with in situ combustion processes initiated by the reaction of pyrophoric materials such as linseed oil and cobalt naphthenate in the presence of air or similar oxidizing agents. It may be employed in conjunction with wellbore heaters used for well stimulation, dehydration of swelling clays and other purposes. It can be utilized in connection with steam and hot water injection processes employed for secondary recovery. It may find application for controlling the flow of the combustion gases at the producing wells during in situ combustion operations. It can be used in waterflood secondary recovery operations to direct the Water to the proper zone in a wellbore drilled through a multizone reservoir. In this case, the bimetallic strips will be arranged With the metal having the highest coefficient of thermal expansion on the outside so the cooling effect of the injected water will cause contraction and outward movement of the bimetallic strips to set the packer. When the device is utilized in conjunction with a wellbore heater as mentioned above, the cantilever bimetallic strips and sealing element will generally be positioned on the outer surface of the heater above the heating element therein. The heater itself thus serves as the supporting structure.

FIGURE 4 of the drawing depicts a heater provided with a packer actuated by bimetallic elements in accordance with the invention. As shown in FIGURE 4, heater 32 has been lowered within casing 33 to a point opposite perforations 34 by means of self-supporting electrical cable 35. The cable is affixed to the heater and is connect-ed to an internal resistance element not shown. Bimetallic strips 36, similar to those depicted in FIGURES 1 through 3 of the drawing, are Welded. bolted or otherwise aflixed at one end to the outer surface of the heater above the heating element. The strips are arranged in cantilever fashion so that an increase in the temperature of the heater will result in movement of the lower ends of the strips outwardly away from the heater. An annular sealing element 37 of asbestos or similar flexible, heat-resistant material is mounted on the outer surface of the heater above the bimetallic strips and is held in place by annular member 38 which may be welded or otherwise bonded to the outer surface of the heater. When the heater is energized, sealing element 37 is forced outwardly into contact with the borehole casing to effect a seal. The packer of the invention may thus be utilized with a variety of conventional Wellbore heaters of the electrical or combustion type. Such heaters are available from a number of commercial sources and will be familiar to those skilled in the art.

A further embodiment of the invention in which bimetallic elements are arranged upon the supporting structure in a somewhat different manner from that described above is shown in FIGURES 5 and 6 of the drawing. Referring to FIG. 5, reference numeral 20- designates the lower end of a section of production tubing positioned within casing 21 in a wellbore. Fixed on the outer surface of tubing 20 is upper supporting member 22 to which bimetallic strips 23 are attached at their upper ends. The upper supporting member is preferably a ring welded or otherwise attached to tubing 20 as indicated by reference numeral 24. Gasket inserts may be provided between the ends of the strips on member 22, if necessary, to assure a fluid-tight seal between them. At their lower ends bimetallic strips 23 are attached to lower supporting member 25 which is free to slide upwardly with respect to tubing 20, shoulder 26 on the tubing below the assembly preventing downward movement. The strips utilized may be similar in composition to those described in conjunction with the previous embodiment.

As shown in FIG. 6 of the drawing, bimetallic strips 23 are spaced evenly around the apparatus. Each strip curves outwardly from the upper and lower supporting members. The metal having the greatest coefficient of thermal expansion is placed on the outer face of each strip so that the strips will move out still further with increased temperature. Since the lower supporting element is free to move upwardly with respect to tubing 20, the strips can expand without high stresses being set up. Flexible sealing element 27 made of rubber, asbestos, plastic or similar material is positioned over the outer surface of bimetallic strips 23 and is held in fluidtight relationship at the upper and lower ends of the as- 6 sembly by upper retainer 28 annd lower retainer 29, respectively. Bolts 30 and 31 or similar means are provided for holding the retainer, bimetallic strips and sealing element in place on the supporting members. The sealing element is shaped to permit its expansion against the borehole or wellbore wall.

Operation of the apparatus depicted in FIGURES 5 and 6 of the drawing is generally similar to that of the previous embodiment. An increase in the temperature of bimetallic strips 23 of the apparatus causes the strips to expand outwardly, since both ends are constrained, forcing sealing element 27 against the borehole or wellbore wall and effecting a seal. The temperature rise necessary to actuate the assembly can be controlled over a wide range by varying the composition of the bimetallic strips, by varying the length of the strips, and by varying the distance through which the strips must move in order to force the sealing element into a closed position. The use of relatively long strips positioned on supporting members some distance apart permits considerable movement with only a moderate temperature rise and hence this embodiment of the invention may be preferred where very high temperatures are not utilized. Cooling of the device results in contraction of the bimetallic elements and retraction of the sealing elements so that the packer assembly can be withdrawn from the borehole, or wellbore.

The invention in certain aspects is particularly adapted to use in conjunction With in situ combustion operations and has been discussed primarily from the standpoint of such operations. It will be apparent, however, that the thermodynamic packer assembly is not limited to in situ combustion processes and may be utilized in a variety of down-hole operations where a packer must be set in place. In many instances it will be convenient to combine the packer assembly with an electrical heating element or similar unit. Such a unit may be suspended on a wire line and may have the packer assembly mounted directly on the heater. Bimetallic strips arranged in spiral fashion around the supporting structure may also be used. These and other modifications of the apparatus will readily suggest themselves to those skilled in the art.

What is claimed is:

l. A packer assembly comprising a supporting member which can be lowered into a borehole; a plurality of bimetallic strips attached to the outer surface of said supporting member at points about the periphery of said member, each strip comprising two dissimilar metals bonded together to obtain outward deflection of said strip in response to a change in temperature; and a flexible sealing element mounted on said supporting member in fluidtight relationship to said member, said sealing element extending about said supporting member over the outer surfaces of said bimetallic strips.

2. Apparatus as defined by claim 1 wherein said bimetallic strips are attached at one end to said supporting member and extend downwardly about said member.

3. Apparatus as defined by claim 1 wherein said bimetallic strips are attached to said supporting member with the metal having the greater coeflicient of thermal expansion on the inner surface of each strip.

4. Apparatus for closing off the annulus of a borehole Which comprises a tubular supporting member provided with means at the upper end for attaching said member to a string of pipe; a plurality of bimetallic strips attached to the outer surface of said supporting member and extending downwardly about said member, each strip comprising two dissimilar metals bonded together to obtain outward deflection of said strip in response to a change in temperature; and a flexible annular sealing element mounted on said supporting member in fluid-tight relationship to said member, said sealing element extending downwardly about said supporting member over the outer surfaces of said bimetallic strips.

5. Apparatus as defined by claim 4 wherein an upper portion of said supporting member extends outwardly above said sealing element and limits movement of said sealing element and said bimetallic strips with respect to said supporting member.

6. Apparatus for closing off a borehole comprising a wellbore heater containing an electrical heating element; a plurality of bimetallic strips mounted on the outer surface of said heater above said heating element, said strips extending downwardly about said heater and each strip comprising two dissimilar metals bonded together to obtain outward deflection of said strip in response to heat from said heating element; and a flexible sealing element mounted on said heater above said bimetallic strips, said sealing element extending downwardly about said heater over the outer surfaces of said bimetallic strips.

References Cited in the file of this patent UNITED STATES PATENTS 1,998,915 Young Apr. 23, 1935 10 2,843,052 Andrus July 15, 1958 2,942,668 Maly et a1 June 28, 1960